The invention relates to a device for intermingling a bundle of wet threads of smooth multifilament in a turbulent air stream. The device includes a nozzle body with U-shaped thread channels and a centered inlet or bore hole for compressed air assigned to each thread channel. The invention further relates to a process for intermingling the bundle of threads in a turbulent air stream.
In order to obtain good weaving properties of smooth textile multifilament threads, a sizing is usually required. Intermingling the threads in a turbulent air stream supports the sizing effect so that the weaving properties are improved or the degree of sizing can be maintained at a lower level. The turbulent air stream treatment serves to keep the fibrils close enough to each other so as to permit a gluing by the sizing agent. Weak knots of air serve this purpose, especially if the turbulent air stream treatment is performed directly before the sizing trough, since there is little stress applied to the threads and only a few knots are lost. Weak knots of turbulent air in short, regular distances are more appropriate than stronger knots in larger and thus irregular distances. Stronger knots also present the risk of showing traces in the fabric.
The knots can be influenced by the diameter of the thread channel. A large thread channel results in tight knots of air in relatively large distances; a small diameter results in more loose knots in smaller, more regular distances.
Stretch-sizing of multifilament threads made of thermoplastics, especially made of polyamide and polyester but also polyethylene and polypropylene, employs a wet thread which is treated in a turbulent air stream between a stretching trough, usually containing water, and a sizing trough; the adherent water is blown off during the air stream treatment using a suitable device.
The diameter of the thread channel influences the air stream treatment; while it has to be narrow to blow off the water with a minimum of air, there is a restriction in selecting the kind of turbulent air stream treatment of wet threads. While relatively loose knots are sufficient to support the sizing effect, this will not be a disadvantage to the stretch sizing, where the threads are hardly exposed to stress between the turbulent air stream treatment and the sizing trough.
Devices for intermingling a bundle, of threads made of dry filament threads in a turbulent air stream are known (U.S. Pat. No. 4,644,622). The known device includes a rotatable nozzle body, provided with tube-like turbulence nozzles each having a slot; these nozzles are closed during operation. The thread guiding channel is rectangular, and the thread is guided diagonally in this thread channel. This device is appropriate for the treating of certain titers of dry threads in a turbulent air stream during the warping or stretch-warping process. There is no information provided on the efficiency and the turbulence device and its air consumption. A disadvantage is the time-consuming inserting of the bundle of threads.
From the EP-A 0 121 010 a turbulence device with turbulence nozzle is known for the manufacture of an interlaced yarn. The device is equipped with a U-shaped turbulence channel. Although the turbulence improved, the consumption of compressed air is still much too high.
EP-A 0 144 617 describes a process for the manufacture of a chain which includes stretching in a water bath, followed by a turbulent air stream treating, and a subsequent sizing process. The description does not give any details on the kind of turbulence involved.
It is a disadvantage of the known wet stretching process that the liquid adherent to the thread must be mostly removed before entering the turbulent air stream device in order to prevent a dilution of the sizing liquor. This is achieved by an upstream system of squeeze rolls. A squeezer disposed downstream of the stretching trough removes the water only insufficiently, i.e., only about 50% of the water is removed.
All known nozzles have disadvantages. They use too much air or damage the thread. Most of the turbulence nozzles operate with dry threads, achieving satisfactory results in a certain titer range. Employing wet threads, however, leads to a rapid efficiency decrease due to the fact that the water is removed insufficiently, resulting from an insufficient turbulence of the bundle of threads.
Another disadvantage of the known turbulence devices is that each individual thread must be carried into the eyes and combs before and after the thread channels, which is very time-consuming.